Contact operating means for air blast circuit breaker



Jan. 21, 1964 'H. FORWALD CONTACT OPERATING MEANS FOR AIR BLAST CIRCUIT BREAKER Filed NOV. 27, 1961 1 I0 Q 2 1/ d Ila I Q: m m

IN VEN TOR. $4id/V 5/ w4// w w w United States Patent 3,118,996 CONTACT OPERATING MEANS FOR AIR BLAST CIRCUIT BREAKER Haakon Forwald, Ludvika, Sweden Filed Nov. 27, 1961, Ser. No. 155,047 Claims priority, application Sweden Dec. 15, 1960 3 Claims. (Cl. 200-148) This invention relates to a novel operating mechanism for the movable contact of an air blast circuit breaker, and more specifically relates to a novel operating mechanism wherein the movable contact is temporarily stopped or slowed down in its motion toward its fully disengaged position at a distance from the cooperating stationary contact which is most favourable for are interruption.

Operating mechanisms for controlling the motion of a movable contact in the above manner are well known to the art. Such mechanisms, however, generally comprise several parts and several control valves.

The present invention provides a novel structure for temporarily halting the movable contact in its opening motion which requires a relatively simple throttled pneumatic connection between a high pressure chamber which contains the cooperating contacts and a first volume limited by one side of the operating piston which operates the movable contact. The other side of the piston limits a second volume and connection of this volume to compressed air causes the contacts to disengage. Thus, during the first part of the opening movement of said piston, the pressure in said first volume is built up and imparts a limiting force to said piston to slow the movable contact motion at a point which is most favourable for are extinction.

Accordingly, a primary object of this invention is to provide a novel reliable operating mechanism for the movable contact of an air blast circuit breaker.

Another object of this invention is to provide a novel cooperation between the pressures within the interrupter chamber of an air blast circuit breaker and the pressures applied to the operating piston of the movable contact of the circuit breaker so that the movable contact is temporarily braked at a position most favourable for circuit interruptions.

These and other objects of this invention will become apparent from the following description when taken in connection with the drawings, in which:

FIGURE 1 shows a cross-sectional view of the interrupter of an air blast circuit breaker constructed in accordance with the present invention.

FIGURE 2 shows a modification of the interrupter of FIGURE 1.

Referring now to FIGURE 1, I have illustrated therein an interrupter chamber 1 (partially shown) which is closed and permanently filled with at least enough compressed air for a single circuit interruption operation.

An insulating bushing enters chamber 1 and has the stationary contact 3 mounted thereon preferably in a resilient manner. The wall of container 1 is then secured to a mechanism housing 2 which carries the operating mechanism for moving a movable contact 4 with respect to stationary contact 3. The movable contact 4 is more specifically connected to a piston rod 5 which terminates on a piston 6. A first side of piston 6 encloses volume 7, while the other side of piston 6 encloses a second volume 8.

An air blast channel 9 then passes through the movable contact 4 in the usual manner, and is connected to open air through openings 10 in the mechanism housing 2. Piston rod 5 further carries a valve plate 11, the opposing surfaces of which can be provided with any appropriate gasketing material, whereby the valve plate 11 3,118,996 Patented Jan. 21, 1964 can seat on the annular protrusion 11a carried from mechanism housing 2 to close the blast channel '9 when the movable contact is in the closed position shown in FIGURE 1.

The opposite surface of plate 11 will close against the openings 10 when the movable contact 4 moves to its completely disengaged position. The movable contact is normally biased to the closed position by means of biasing spring 12 which alternatively could have been contained within volume 7, rather than the interrupter chamher.

A conduit 13 then places volume 7 in communication with container 1 through a valve 14 which is biased to the closed position by a biasing spring 1411. The valve 14 has an orifice 15 therethrough to permit controlled leakage from volume 7 to container 1.

In order to operate movable contact 4 to the disengaged position, a conduit 16 connected to volume 8 is connected to high pressure air through an appropriate valve means (not shown). When conduit 16 is exposed to high pressure air, the piston 6 will be moved upwardly to move contact 4 to a disengaged position. This motion originally takes place with relatively high speed with an are being drawn between contacts 3 and 4. At this time, however, the blast valve formed by valve plate 11 has been opened so that compressed air will flow out of chamber \1 and through the are at high velocity with the arcing products being exhausted through channels 10.

Once the movable contact 4 reaches an opening distance with respect to stationary contact 3 where most effective are extinction will occur, the air in volume 7 which was originally at the same pressure as the air within container 1, will be sufficiently compressed by piston 6 to exert a considerable opposing force to the motion of piston 6. Thus, the movable contact 4 will be temporarily halted or slowed down considerably at the point of most e-fficient arc interruption. At the same time, and because of the connection through orifice 15 of volume 7 and the interrupter container, the pressure in volume 7 will gradually decrease (the air blast operation at least partially exhausting the pressure within container 1). Thus, the movable contact moves slowly upwardly until it reaches a fully open position with the openings 10 being closed by the valve plate 11.

In order to close the interrupter, the conduit 16 is connected to open air. Thus, the pressure below piston 6 immediately decreases, and the pressure within container 1, which has now been built up to its rated pressure, will quickly open valve 14 and flow into volume 7. Thus, the movable contact will be very rapidly moved to its closed position shown in FIGURE 1.

It is to be noted that in the arrangement of FIGURE 1 a blast of air will be produced during the closing process. Thus, pre-closing arcs drawn will be effectively cooled.

Moreover, it will be seen that the construction of FIG- UR=E 1 does not require mechanisms having a plurality of relatively movable parts so that good contact synchronization for both opening and closing can be achieved when several series connected interrupters are used.

A second embodiment of the invention is shown in FIGURE 2 wherein components similar to those of FIG- URE 1 have been given similar identifying numerals. In FIGURE 2 the conduit 13 is additionally provided with a throttle valve 17 which is connected in parallel with one-way valve 18, and permits a controlled flow of compressed air between container 1 and volume 7.

An opening 20 is also placed in the wall of the cylinder which includes volume 7 where the opening 21} is in communication with conduit '13 by means of a pressure equalizing channel 19. A back valve 21 which permits free flow of air from volume 7 to conduit 13 is then arranged in series With pressure equalizing channel .19. The opening 20 is so arranged that it will be closed by piston 6 with respect to volume 7 when the movable contact 4 has reached the desired distance from stationary contact 3 which is most efficient for arc interruption.

In operation of the system of FIGURE 2, the mechanism will be operated by applying compressed air to conduit 16. The piston 6 and the contact 4 connected thereto will, therefore, be moved rapidly upwardly. The air in volume 7 will initially flow out through pressure equalizing channel 19 so that no significant impedance will be applied to the motion of piston 6 during this initial stage. When, however, opening 20 is closed by the piston 6 with respect to volume 7, the pressure in volume 7 will be rapidly increased, and the motion of piston 6 will be checked momentarily while arc interruption occurs within container 1.

Pressure equalization between the chamber 1 and volume 7 then occurs by means of the throttling valve 17 and the movable contact is moved relatively slowly toward-its fully opened position.

In order to close the contacts 3 and 4 of FIGURE 2, the pressure in conduit 16 is exhausted as in FIGURE 1. However, in the device of \FIGURE 2, compressed air cannot flow into the operating volume 8 of piston 6 because of valve 21.

In each of the embodiments of FIGURES 1 and 2, it will be noted that the impact of the movable contact during closing will be taken up by the mechanism housing rather than by the bushing, as has been the case in the past. That is to say, stationary contact 3 is mounted resiliently with respect to its bushing. Thus, the closing impact will be taken up by the stationary sealing surfaces in the mechanism housing.

Although this invention has been described with respect to its preferred embodiments it should be understood that many variations and modifications will now be obvious to those skilled in the art, and it is preferred, therefore, that the scope of this invention be limited not by the specific disclosure herein but only by the appended claims.

I claim:

1. An air blast circuit breaker comprising a container for receiving compressed air, a stationary contact secured within said container and a movable contact movable into and out of engagement with respect to said stationary contact; an operating piston; said operating piston being secured to said movable contact; said operating piston being disposed within a cylinder; said operating piston dividing said cylinder into a first and second space; a conduit means; said conduit means connecting said first space to said container; said conduit means containing a valve means; said second space being selectively connectable to a high pressure operating system or open air whereby connection of said second space to high pres sure air moves said piston to cause contact disengagement between said first and second contacts; the pressure in said first space being built up during the first part of the movement of said piston during contact disengagement; said built up pressure imparting a limiting force to said piston whereby said main contact is retained at a favourable interruption distance with respect to said stationary contact; said piston and said movable contact being thereafter relatively slowly moved to a fully open position, said cylinder having a pressure equalizing channel connecting said cylinder with said container; said pressure equalizing channel permitting free communication between said first space and said container during a first part of an opening motion of said piston and until said movable contact reaches its said favourable interruption distance.

2. The device substantially as set forth in claim 1 wherein said piston moves into blocking relationship with respect to said pressure equalizing channel when said suitable interruption distance is reached and thereafter cuts oil the connection between said first space and said pressure equalizing channel.

3. The device substantially as set forth in claim 1 which includes a second back-valve means connected in said pressure equalizing channel to block passage of high pressure air from said container through said pressure equalizing channel.

References Cited in the file of this patent UNITED STATES PATENTS 2,574,334 Latour Nov. 6, 1951 2,766,348 Forwald Oct. 9, 1956 2,881,291 Forwa'ld Apr. 7, 7959 2,919,329 Latour Dec. 29, 1959 2,922,010 Cromer et a1 Jan. 19, 1960 FOREIGN PATENTS 529,456 Germany July 13, 1931 

1. AN AIR BLAST CIRCUIT BREAKER COMPRISING A CONTAINER FOR RECEIVING COMPRESSED AIR, A STATIONARY CONTACT SECURED WITHIN SAID CONTAINER AND A MOVABLE CONTACT MOVABLE INTO AND OUT OF ENGAGEMENT WITH RESPECT TO SAID STATIONARY CONTACT; AN OPERATING PISTON; SAID OPERATING PISTON BEING SECURED TO SAID MOVABLE CONTACT; SAID OPERATING PISTON BEING DISPOSED WITHIN A CYLINDER; SAID OPERATING PISTON DIVIDING SAID CYLINDER INTO A FIRST AND SECOND SPACE; A CONDUIT MEANS; SAID CONDUIT MEANS CONNECTING SAID FIRST SPACE TO SAID CONTAINER; SAID CONDUIT MEANS CONTAINING A VALVE MEANS; SAID SECOND SPACE BEING SELECTIVELY CONNECTABLE TO A HIGH PRESSURE OPERATING SYSTEM OR OPEN AIR WHEREBY CONNECTION OF SAID SECOND SPACE TO HIGH PRESSURE AIR MOVES SAID PISTON TO CAUSE CONTACT DISENGAGEMENT BETWEEN SAID FIRST AND SECOND CONTACTS; THE PRESSURE IN SAID FIRST SPACE BEING BUILT UP DURING THE FIRST PART OF THE MOVEMENT OF SAID PISTON DURING CONTACT DISENGAGEMENT; SAID BUILT UP PRESSURE IMPARTING A LIMITING FORCE TO SAID PISTON WHEREBY SAID MAIN CONTACT IS RETAINED AT A FAVOURABLE INTERRUPTION DISTANCE WITH RESPECT TO SAID STATIONARY CONTACT; SAID PISTON AND SAID MOVABLE CONTACT BEING THEREAFTER RELATIVELY SLOWLY MOVED TO A FULLY OPEN POSITION, SAID CYLINDER HAVING A PRESSURE EQUALIZING CHANNEL CONNECTING SAID CYLINDER WITH SAID CONTAINER; SAID PRESSURE EQUALIZING CHANNEL PERMITTING FREE COMMUNICATION BETWEEN SAID FIRST SPACE AND SAID CONTAINER DURING A FIRST PART OF AN OPENING MOTION OF SAID PISTON AND UNTIL SAID MOVABLE CONTACT REACHES ITS SAID FAVOURABLE INTERRUPTION DISTANCE. 